-- type Set
-- type Point

-- function Intersection : Set a * Set b -> Set
-- function Subset : Set a * Set b -> Set

-- predicate Intersect : Set s1 * Set s2
-- predicate NotIntersecting : Set s1 * Set s2
predicate IsSubset : Set s1 * Set s2
-- predicate NotSubset : Set s1 * Set s2
-- predicate PointIn : Set s * Point p
-- predicate PointNotIn : Set s * Point p
